I know that Undertow figure it out a content-length or transfer-encoding header when none of them was set. That's good and it works as expected.

 It seems to be a problem when you explicitly set the "Transfer-Encoding" header bc Undertow, still add the Content-Length (on small responses?) but it doesn't remove the Transfer-Encoding header.

 On such cases, the response contains both headers, which I think it's wrong, no?

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